Field of the Invention
The invention relates to a lubrication unit for lubricating drive and driven members used in a film feed apparatus which continuously feeds a film in a small size motion picture camera, a motion picture projector, a still camera incorporating a motor drive or the like.
The drive and driven members used in a film feed apparatus for continuously feeding a film in a small size motion picture camera, a motion picture projector, a still camera incorporating a motor drive or the like comprise cam, gear, rotary shaft and the like. The cam may be an eccentric cam, a triangular cam or the like which is driven for rotation and provides a lift which is utilized to operate a film feed pawl member which intermittently feeds a strip such as a film or the like. Because the space involved with the cam and the feed pawl is extremely limited and because the cam is subject to an eccentric rotating motion, it is very difficult, if not impossible, to mount an external lubrication unit adjacent to such location. In addition, these members represent an area which is subject to an intermittent load of very high magnitude during the film feeding operation and which is of greatest importance in maintaining the stability of a photographed or projected picture.
The prior art method to provide lubrication to these parts include (1) provision of an oil impregnated felt in sliding contact with the cam, (2) formation of the eccentric cam from an oil impreganted alloy, (3) formation of the cam by molding, (4) use of bearing lubrication method, or the like, none of which provide a satisfactory lubrication as will be discussed below particularly when the cam is subjected to a high speed rotation.
Dealing with the prior art methods more specifically, the first method provides an oil impregnated felt adjacent to the eccentric cam so that lubrication to the sliding surface of the cam is supplied once during every rotation of the cam, but requires a space for the provision of the oil impregnated felt, which it is difficult to supply in the limited space as mentioned above. In addition, it suffers from the disadvantage that the required construction is complex. The second method uses an eccentric cam made of an oil impregnated alloy and does not require an external lubrication means, but the hardness of the oil impregnated alloy is limited, which prevents the manufacturing of the cam from a material having a high hardness, thus rendering it prone to abrasion to cause a gradual decrease in the accuracy of its engagement with the driven member, thereby losing the stability in the film feeding operation. In addition, a high accuracy is difficult to achieve when machining the cam. The third method involves the use of a molded cam, which avoids the need for lubrication as used with a metal cam, but such molded cam is susceptible to deformation under high loads, and does not provide sufficient accuracy in view of its hardness. The fourth method applies an oil of the kind such as grease to the cam surface previously, so that heating and abrasion can be prevented until the grease is lost. Because it is impossible to provide an initial supply of a large amount of grease applied thereto, the cam will progressively experience shortage of lubricant and undergo the resulting seizure of the sliding parts, thus resulting in the decrease of the accuracy of engagement because of abrasion and breakage and causing instability in the film feeding operation. This could be avoided by increasing the contact surface of the cam, which requires a large space and is difficult to provide because of the limited machining accuracy.
The above-mentioned lubrication methods afforded certain achievements at a drive speed of the prior art motion picture camera or motion picture projector (for example, on the order of 8 to 36 frames per second in a motion picture camera), but recently a further increase in the speed has been demanded as a result of diversification of products and explored marketability, and it has become necessary to provide a photographing speed of 72 frames per second or higher in a small size motion picture camera. In these circumstances, the prior art lubrication methods presented problems in view of the adverse influence caused by the seizure of the cam surface, abrasion, and scattering of grease.
Also with gear or rotary shaft, the space provided for these members is extremely limited and because the gear has a concave and convex configuration on it outer periphery while the rotary shaft has very close clearance between it and its bearing, it is very difficult to provide an external lubrication unit adjacent to such parts. In addition, these members are subject to a high torque during the drive, and if they are not properly lubricated, abnormal clicks will occur and regular rotation from the drive will not be obtained, thereby adversely influencing the photographed or projected picture. The lubrication technique and unit as used with the cam mentioned above have been also applied to provide the lubrication of these parts, but the result cannot be said to be satisfactory.